The present invention relates to a method of driving an elevator or other like installation.
More precisely, the invention relates to means enabling the up and down movement of the elevator or the like to be controlled.
In the present patent application, the term xe2x80x9celevator or the likexe2x80x9d covers all kinds of platform or cage known as elevators, lifts, hoists, etc. for moving goods or people between levels, including those designed specifically for the handicapped.
The present invention serves mainly to reduce energy consumption, which is important for the user since it requires less energy on each start, and thus an electrical installation that is smaller. This important detail is but one of the aspects of the invention developed below.
As is well known, there are two large families of drive device for controlling the up and down movements of an elevator, said devices being either electrical or hydraulic. The present invention relates solely to the field of elevators that are controlled in hydraulic manner. Naturally, hydraulic control covers means fed with any liquid, not necessarily water.
Conventionally, in hydraulic type elevator drive systems, there is an actuator whose stroke serves to move the cage, and to do so over an amplitude that is naturally equal to the height of the shaft.
For example, it is easily understood that in order to carry eight people, a 630 kg apparatus is required, and that is the type of apparatus that is the most widespread throughout the world, covering 80% of the market. The dead weight of the structure for an 630 kg cage is approximately equal to the payload, depending on manufacturer, giving a total of about 1260 kg to be moved.
In the two modes mentioned above, energy requirements on starting, and throughout all displacement stages, whether at high speed or at low speed or at approach speed, are large. Heretofore, no energy recovery means has been implemented, and indeed it is clear that the size of the energy consumption bill paid by the user is of little concern to the manufacturer.
Another non-negligible negative feature of known hydraulic systems, and one that is perceived by all users, is the waiting time after the gate of the cage has been closed, given that the elevator remains stationary for a few seconds for the simple reason that the pump cannot start directly delivering the power required, and the drive motor needs to start progressively via a star-delta coupling, and only subsequently put the hydraulic circuit under pressure. It should be observed that this stage is repeated on each upward start of the apparatus.
Existing hydraulic apparatuses enable the user to travel down with the apparatus even in the event of a power failure, which is naturally highly advantageous and very reassuring. The present invention provides a considerable improvement to this advantage.
To achieve this end, the present invention thus provides implementing an energy recovery device and making a fundamental modification to the hydraulic circuit used in the known system.
The invention relates to a drive device for a hydraulic type elevator, the device comprising an actuator cylinder in which a piston is slidably mounted and having a pressure chamber connected via a hydraulic circuit to a pump driven by a motor and connected to a source of fluid.
According to the invention, the device is characterized by the fact that the fluid source is constituted by a pressure accumulator, and by the fact that the hydraulic circuit comprises:
a down duct connecting the pressure chamber to the inlet of the pump and in which there are connected in series a first electrically controlled valve and a first check valve;
an up duct connecting the outlet of the pump to the pressure chamber, and in which there are connected in series a second electrically controlled valve and a second check valve;
a first parallel duct connecting the pressure accumulator to the down duct at a point situated between the first check valve and the inlet to the pump, and in which a third electrically controlled valve is connected; and
a second parallel duct connecting the pressure accumulator to the up duct at a point situated between the second electrically controlled valve and the outlet from the pump, and in which a fourth electrically controlled valve is connected;
by the fact that the first electrically controlled valve and the third electrically controlled valve are open while the elevator is moving downwards, the second electrically controlled valve and the fourth electrically controlled valve then being closed; and
by the fact that the second electrically controlled valve and the fourth electrically controlled valve are open while the elevator is moving upwards, the first electrically controlled valve and the third electrically controlled valve then being closed.